It turns out that some Nexus One owners running CyanogenMod 6 (CM6) have been experiencing issues when trying to update a handful of system apps. As such, XDA-Devs forum member unforgiven512 has thrown the updates into a tidy package. The updated apps are:

Amazon MP3

Google Maps

Google Search

Google Voice

ROM Manager

Street View

Superuser

TalkBack

Twitter

Voice Search

Not only does this fix the app updating bug, but it moves the app info from the "data" partition to the "system" partition.